Electrochemical polymerization of 5-cyanoindole in mixed electrolytes of boron trifluoride diethyl etherate and diethyl ether

High quality poly(5-cyanoindole) (P5CI) films were electrosynthesized by direct anodic oxidation of 5-cyanoindole on stainless steel sheet in the mixed electrolytes of boron trifluoride diethyl etherate (BFEE) and diethyl ether (EE) (by volume 1:1) + 0.05 mol L-1 Bu4NBF4. The film formed can be peeled off the electrode into freestanding films. The addition of EE into BFEE can improve the solubility of monomer. P5CI films obtained from this medium showed excellent electrochemical behavior with conductivity of 10(-2) S cm(-1). Structural studies showed that the polymerization of 5-cyanoindole occurred at the 2,3 position. As-formed P5CI films were thoroughly soluble in strong polar organic solvent dimethyl sulfoxide (DMSO) while partly soluble in tetrahydrofuran (THF) or acetone. Fluorescence spectral studies indicated that P5CI was a good blue-light emitter.